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I don't know if my questions have already been answered. I looked couldn't find it, so here goes. I'm planning on building (2) 4' X 24" X 24" Titan 48s with a single Eminence 3015 speaker per cabinet. I understand that the speaker is 450 RMS/900 max. However, my smallest amp is a QSC 3602. I also just bought a DBX drive rack PA2. I've never owned a drive rack. Are there any special or particular safe settings limits on either or both units to help protect the speaker?
The QSC 3602 in (Stereo Mode) is rated at ◦8 Ohms FTC 20 Hz - 20 kHz 0.05% THD: 725 Watts
◦8 Ohms EIA 1 kHz 0.1% THD: 775 Watts. I don't know how accurate those numbers are, but I do know I shouldn't need to turn the attenuator beyond half way since the sub only needs 4 to 500 to put out the SPL that I want as a mobile dj.

Hook up a voltmeter, feed your mixer with a sine wave tone within the sub's passband, and turn the limiter down until you cannot exceed the max voltage listed in the plans for the driver you used. That's basically it!

It's Majik Ent. wrote:I don't know if my questions have already been answered. I looked couldn't find it, so here goes. I'm planning on building (2) 4' X 24" X 24" Titan 48s with a single Eminence 3015 speaker per cabinet. I understand that the speaker is 450 RMS/900 max. However, my smallest amp is a QSC 3602. I also just bought a DBX drive rack PA2. I've never owned a drive rack. Are there any special or particular safe settings limits on either or both units to help protect the speaker?
The QSC 3602 in (Stereo Mode) is rated at ◦8 Ohms FTC 20 Hz - 20 kHz 0.05% THD: 725 Watts
◦8 Ohms EIA 1 kHz 0.1% THD: 775 Watts. I don't know how accurate those numbers are, but I do know I shouldn't need to turn the attenuator beyond half way since the sub only needs 4 to 500 to put out the SPL that I want as a mobile dj.

It seems you have the plans.

Have a look at the heading "Protecting your drivers".
You'll see the voltage limit for the 3015lf is 60V. That's a displacement limit setting and is required in horn loaded cabs so drivers aren't blown. Displacement limit settings are not the same as those stated for RMS/max specs for drivers.
Displacement limit settings are made with your "brick wall" limiter, in your case the PA2.

As already stated, this setting is made by using a voltmeter on the amp, not some calculation (Watts are a calculation, the product of volts and amps).

Since the PA2 will determine maximum output, leave your attenuators on full, always.
Your master outputs/faders on your mixer will determine overall volume at your gigs.

As for the QSC 3602 being adequate, yes it is, just.
725W/8ohms gives an anticipated output in volts of 76V.
Your limit for the 3015lf in the T48, once again, is 60V.
So you have 16V to spare, so to speak.

Since you say you're not going to play loud, ie to max output, that amp should be fine.
However, if you do some gigs that will have you approaching max output for your T48's, having only 16V above your max output limit for the amp means you are running the amp pretty much to it's limits and that's not good for the amp, especially for prolonged periods. At that volume, it may take the amp to clipping, or thermal shutdown, which you want to avoid.

If you plan to ever run your cabs to war volume, I would consider a more powerful amp.

Just to clarify, voltmeter is set to AC volts, with NO cabs connected.
You measure max voltage output, and one would suspect that reading would be around 76V.
Then decrease the voltage with the limiter...

Grant Bunter wrote:

It's Majik Ent. wrote:I don't know if my questions have already been answered. I looked couldn't find it, so here goes. I'm planning on building (2) 4' X 24" X 24" Titan 48s with a single Eminence 3015 speaker per cabinet. I understand that the speaker is 450 RMS/900 max. However, my smallest amp is a QSC 3602. I also just bought a DBX drive rack PA2. I've never owned a drive rack. Are there any special or particular safe settings limits on either or both units to help protect the speaker?
The QSC 3602 in (Stereo Mode) is rated at ◦8 Ohms FTC 20 Hz - 20 kHz 0.05% THD: 725 Watts
◦8 Ohms EIA 1 kHz 0.1% THD: 775 Watts. I don't know how accurate those numbers are, but I do know I shouldn't need to turn the attenuator beyond half way since the sub only needs 4 to 500 to put out the SPL that I want as a mobile dj.

It seems you have the plans.

Have a look at the heading "Protecting your drivers".
You'll see the voltage limit for the 3015lf is 60V. That's a displacement limit setting and is required in horn loaded cabs so drivers aren't blown. Displacement limit settings are not the same as those stated for RMS/max specs for drivers.
Displacement limit settings are made with your "brick wall" limiter, in your case the PA2.

As already stated, this setting is made by using a voltmeter on the amp, not some calculation (Watts are a calculation, the product of volts and amps).

Since the PA2 will determine maximum output, leave your attenuators on full, always.
Your master outputs/faders on your mixer will determine overall volume at your gigs.

As for the QSC 3602 being adequate, yes it is, just.
725W/8ohms gives an anticipated output in volts of 76V.
Your limit for the 3015lf in the T48, once again, is 60V.
So you have 16V to spare, so to speak.

Since you say you're not going to play loud, ie to max output, that amp should be fine.
However, if you do some gigs that will have you approaching max output for your T48's, having only 16V above your max output limit for the amp means you are running the amp pretty much to it's limits and that's not good for the amp, especially for prolonged periods. At that volume, it may take the amp to clipping, or thermal shutdown, which you want to avoid.

If you plan to ever run your cabs to war volume, I would consider a more powerful amp.

Just to clarify, voltmeter is set to AC volts, with NO cabs connected.
You measure max voltage output, and one would suspect that reading would be around 76V.
Then decrease the voltage with the limiter...

So, higher than 76 v is better? I do have a Crown 6002 as well as a QSC 4050. I will get a volt meter and see what their readings are. I read that the 3602 is 66.7v, but I will check for myself. Thanks for the knowledge share!

whines wrote:Hook up a voltmeter, feed your mixer with a sine wave tone within the sub's passband, and turn the limiter down until you cannot exceed the max voltage listed in the plans for the driver you used. That's basically it!

Thank you for the knowledge share! ☺

So if 16 volts isn't enough headroom, what is? Couldn't he try limiting at 55 volts and if it's still crazy loud, use that? Or 50, etc. I know I've read on here that squeezing those last couple of volts really doesn't add all that much in output. Yes he said he wants to be able to push it to its limit, but until he gets a bigger amp this might get him by.

Rich4349 wrote:So if 16 volts isn't enough headroom, what is? Couldn't he try limiting at 55 volts and if it's still crazy loud, use that? Or 50, etc. I know I've read on here that squeezing those last couple of volts really doesn't add all that much in output. Yes he said he wants to be able to push it to its limit, but until he gets a bigger amp this might get him by.

While the amp may be able to perform like that, it would be much better to have plenty of headroom which will allow the amp to remain cooler due to reduced amperage flow, and thus last much longer.

I'm only putting this out there so that there is that awareness.

Fellas,

That 3602 is a workhorse of an amp. It has plenty of power to handle two T48s per side and not even whimper. I would however, limit the voltage to about 55-6 and keep the high pass at 45hz if you really want to protect them.

If you want to go lower and louder, build a couple more. But, you'll get a lot of thump out of those two at those settings....and you won't blow 'em up.

I run mine off a plx3602, either a pair per channel, or singles on each channel. With the 10ohm rating on the T48 and the power rating of the 3602 it takes quite a bit to damage the drivers, especially if you apply the low-cut filter as recommended. You're probably pretty safe even without the limiting. It's a pretty nice match power-wise. Just keep the amp out of clipping and it should be happy.

Tom Smit wrote:

Rich4349 wrote:So if 16 volts isn't enough headroom, what is? Couldn't he try limiting at 55 volts and if it's still crazy loud, use that? Or 50, etc. I know I've read on here that squeezing those last couple of volts really doesn't add all that much in output. Yes he said he wants to be able to push it to its limit, but until he gets a bigger amp this might get him by.

While the amp may be able to perform like that, it would be much better to have plenty of headroom which will allow the amp to remain cooler due to reduced amperage flow, and thus last much longer.

I'm only putting this out there so that there is that awareness.

Agreed Tom.

Also so it's out there, you can have to much power in an amp.
When you have to much power in an amp is dictated by the ability of your limiter's ability to reduce the voltage.

You don't want the limiter to be constantly engaging as you turn the volume up on your faders...

Also so it's out there, you can have to much power in an amp.
When you have to much power in an amp is dictated by the ability of your limiter's ability to reduce the voltage.

You don't want the limiter to be constantly engaging as you turn the volume up on your faders...

This is easily solved by reducing gain in your crossover before the limiter.

BrentEvans wrote: This is easily solved by reducing gain in your crossover before the limiter.

Brent, does this lead to a mismatch between sub and tops levels? Or do you have to reduce the gain in the tops too?

Grant Bunter wrote:

BrentEvans wrote: This is easily solved by reducing gain in your crossover before the limiter.

Brent, does this lead to a mismatch between sub and tops levels? Or do you have to reduce the gain in the tops too?

It all depends on how different the sensitivity of each cab is. Some crossovers have gain stages after the limiter too. Getting gain structure right is just part of the deal.